Global health authorities are scrambling to contain a deadly outbreak of hantavirus linked to the polar expedition ship Hondius, tracing some 30 departed passengers from at least a dozen countries – as well as two flights linked to an ill woman – as epidemiologists investigate how the rare strain made its way onto the ship.

World Health Organization Director Tedros Adhanom Ghebreyesus said in a briefing Thursday that five of the eight reported cases of hantavirus have so far been confirmed, but officials emphasized that the public health risk remains low. Three passengers have died.

The Andean strain is the only type of hantavirus known to spread through prolonged close contact between household members or intimate partners, he said, adding that this “appears to be the case in the current situation.” Still, the number of cases could rise given the incubation period of the virus, he said, which can last up to six weeks.

The ship is en route to the Canary Islands, where the cruise operator said it expects to arrive early Sunday. Physicians from the WHO, the Netherlands, and the European Center for Disease Prevention and Control are on board conducting interviews with each person to assess their exposure and risks, WHO officials said. The WHO is developing a step-by-step plan for how passengers and crew can safely disembark and return home once the ship docks.

Hantavirus is normally linked to exposure to the urine or feces of infected rodents, but the Andes virus has been known to spread between people, WHO officials have said. The organization has said it is working on the assumption the initial patients were infected off the ship, either before they boarded in Argentina or on an excursion.

U.S. officials in at least five states – Arizona, California, Georgia, Texas and Virginia – are monitoring symptoms of seven returning passengers, according to state health officials. None of the travelers have reported symptoms, officials said. Two passengers are in Texas and two are in Georgia, health officials said.

State public health officials in Texas and Georgia say they have contacted and are monitoring individuals who’ve returned home from the cruise. The two people in Georgia and two in Texas show no signs of infection or are not experiencing symptoms, the state health departments said.

“They have agreed to monitor themselves for symptoms with daily temperature checks and contact public health officials at any sign of a possible illness,” a statement from the Texas health department said.

The Trump administration is “closely monitoring the situation,” the Centers for Disease Control and Prevention said in a statement, with the State Department leading a coordinated response that includes direct contact with the passengers. “At this time, the risk to the American public is extremely low,” the CDC said. “We urge all Americans aboard the ship to follow the guidance of health officials as we work to bring you home safely.”

Despite the U.S. withdrawal from the WHO that became effective earlier this year, WHO experts said during the briefing Thursday that they have had excellent technical collaboration with counterparts at the CDC.

Referring to the United States and Argentina, which has also withdrawn from the WHO, Tedros said: “I think they will reconsider their decisions because they can see how important universality is for health security. Because viruses don’t care about our politics, don’t care about borders, don’t care about all the excuses we may have.”

Tom Frieden, a former CDC director, said in a Substack post that the outbreak highlights the importance of international coordination, information sharing and global surveillance to protect against emerging infectious-disease threats. He noted the laboratory testing in South Africa, preparation for port reception in Spain and sequencing of the virus by the WHO.

Frieden said American doctors and public health officials will be relying on the WHO’s expertise in defining cases and exposure windows, as well as contact tracing data, to identify exposed travelers who may have flown through U.S. airports.

“None of this can happen without WHO,” wrote Frieden, president and CEO of Resolve to Save Lives.

In the U.S., the CDC, which in years past has held regular – sometimes daily – briefings during infectious-disease outbreaks, has not held a briefing. A spokesman for the Department of Health and Human Services did not return a request for comment about briefings.

The initial information that American passengers had returned to the U.S. was first reported Wednesday by MedPage Today, a medical news publication.

Public health experts are growing increasingly alarmed about the lack of public communication from the CDC. Questions about where the returned passengers are going and the risk for the public are fair questions in the public’s mind.

“Three people died of a viral disease we have neither treatment nor vaccine for acquired in a setting that millions use (cruise ship),” said Jeanne Marrazzo, chief executive of the Infectious Diseases Society of America and a former director of the National Institute of Allergy and Infectious Diseases. “The information gap created by CDC’s silence is a breach of trust and scientific integrity,” Marrazzo said.

On Thursday, the Dutch Health Ministry said in an emailed statement that a flight attendant is in a hospital and being tested for the virus, declining to elaborate. The Dutch news outlet RTL cited the ministry as saying she had come into contact in Johannesburg with a cruise ship passenger who died of the virus a day later.

A passenger who left the cruise in St. Helena was one of 82 people who boarded an Airlink flight to Johannesburg on April 25. The same day, she boarded a KLM flight to Amsterdam, but the crew decided not to allow her to travel because of her medical condition, the Dutch airline said in a statement. Both airlines are working with health authorities and tracing passengers.

Oceanwide Expeditions said Thursday that it has contacted all 29 guests who disembarked the ship at St. Helena on April 24, before the first case of hantavirus was confirmed. The cruise operator said that included six Americans, but state health department officials report seven passengers who have returned to the U.S.

The second of two medical flights has arrived in the Netherlands, with three individuals – two with symptoms and one asymptomatic – under medical care, the company said. There are no passengers with symptoms on board, it added, with the ship sailing for Tenerife in the Canary Islands. Spanish Health Minister Mónica García said Wednesday that international passengers will be evacuated for repatriation, while Spanish citizens will be taken to a military hospital in Madrid where they will be tested and placed under quarantine if necessary.

Three passengers have died since the outbreak began – two Dutch nationals and a German. Two of them died aboard the ship. A British man is in intensive care in South Africa, and a Swiss man who departed the ship in late April was also confirmed to have the virus.

Several cases have been confirmed to be the Andes virus by health authorities in South Africa and Switzerland, while testing is taking place in other suspected cases in Germany and the Netherlands.

Ruhi Cenet, a Turkish documentary maker who got off the ship in St. Helena, said the company should have considered earlier that the first death on board could have been from an infectious disease.

“It turns out the situation was much worse than we were told,” he said in a video posted on Instagram. “People who may have been carrying the virus should have been quarantined,” he said, adding that meals were eaten together and group excursions continued after the first death was reported.

The outbreak is likely to be challenging to investigate, according to experts with experience in global disease investigations, because the first known patients – a Dutch couple – have died. Key details about how they were exposed may never be known.

By the time the outbreak was recognized, some travelers had already dispersed across countries, boarding commercial flights or moving through multiple ports – a dynamic that can complicate efforts to trace who may have been exposed.

“That’s the big lift,” said Martin Cetron, a former senior CDC official who oversaw global migration and quarantine efforts for more than two decades. Investigators must simultaneously define cases, determine how the virus is spreading and trace contacts, sometimes across multiple countries, to understand the outbreak’s scope.

Argentina’s Health Ministry said the Andean strain has been reported to circulate only in the southern provinces of Chubut, Río Negro and Neuquén, as well as in southern Chile. It is tracing the movements of the Dutch citizens who first presented symptoms. They arrived in Argentina on Nov. 27 and undertook a lengthy trip through the country, including Neuquén province, and also stopped in Chile and Uruguay before departing from Ushuaia in southern Argentina on April 1.

No cases associated with the Hondius outbreak have been reported in Argentina, the health agency said, but teams are heading to Ushuaia to capture rodents and conduct an analysis. In a separate statement this week, the agency said 101 hantavirus cases had been detected in the country this year, including three in one family cluster in which authorities suspect person-to-person transmission.

The cruise had carried 149 people of 23 nationalities, according to Oceanwide Expeditions, coming from places such as Spain, France, the United States, Belgium, New Zealand, Turkey and Argentina. It also had an international crew, with members from the Philippines, Russia, India and Montenegro.

Health authorities in Switzerland and the United Kingdom said Wednesday that some nationals who had left the cruise and their close contacts are isolating following official advice. In the Swiss case, which authorities confirmed to be the Andean variant, the man noticed symptoms upon returning from his trip, while his wife is self-isolating as a precaution.

(c) 2026, The Washington Post · Victoria Craw, Lena H. Sun